Amazing stamina.

I was chatting to jillington yesterday and I mentioned a flower in my garden that flowered in early April and is showing no signs of giving up the fight. I thought you might like to see it. Left is April and right is today, thats six months of constant flowering. So far I have been unable to identify it and I thought that you might be able to solve the mystery. I got quite a few suggestions when I blipped it on April 16th but none of them were right.